Dehydrogenation method and catalytic composite for use therein

ABSTRACT

DEHYDROGENATABLE HYDROCARBONS ARE DEHYDROGENATED BY CONTACTING THEM AT DEHYDROGENATABLE CONDITIONS WITH A CATALYTIC COMPOSITE COMPRISING A COMBINATION OF CATALYTICALLY EFFECTIVE AMOUNTS OF A PLATINUM GROUP COMPONENT, A GERMANIUM COMPONENT, AND AN ALKALI OR ALKALINE EARTH METAL WITH A POROUS CARRIER MATERIAL. A SPECIFIC EXAMPLE OF THE CATALYTIC COMPOSITE DISCLOSED HEREIN IS A COMBINATION OF A PLATINUM COMPONENT, A GERMANIUM COMPONENT, AND AN ALKALI OR ALKALINE EARTH COMPONENT WITH AN ALUMINA CARRIER MATERIAL WHEREIN THE COMPONENTS ARE PRESENT IN AMOUNTS SUFFICIENT TO RESULT IN THE COMPOSITE CONTAINING, ON AN ELEMENTAL BASIS, 0.01 TO 2 WT. PERCENT PLATINUM 0.01 TO 5 WT. PERCENT GERMANIUM, AND 0.1 TO 5 WT. PERCENT OF THE ALKALI OR ALKALINE EARTH METAL.

United States Patent Office 3,47,7l9 Patented Mar. 7, 1972 3,647,719 DEHYDROGENATIGN METHOD AND CATALYTIC COMPOSITE FOR USE THERlElN John C. Hayes, Palatine, 11]., assignor to Universal Oil Products Company, Des Plaines, Ill.

No Drawing. Filed Aug. 21, 1969, Ser. No. 852,104 Int. Cl. B01j 11/12 US. Cl. 252-466 PT 10 Claims ABSTRACT OF THE DISCLOSURE Dehydrogenatable hydrocarbons are dehydrogenated by contacting them at dehydrogenatable conditions with a catalytic composite comprising a combination of catalytically effective amounts of a platinum group component, a germanium component, and an alkali or alkaline earth metal with a porous carrier material. A specific example of the catalytic composite disclosed herein is a combination of a platinum component, a germanium component, and an alkali or alkaline earth component with an alumina carrier material wherein the components are present in amounts sufficient to result in the composite containing, on an elemental basis, 0.01 to 2 wt. percent platinum, 0.01 to wt. percent germanium, and 0.1 to 5 wt. percent of the alkali or alkaline earth metal.

The subject of the present invention is broadly an improved method for dehydrogenating a dehydrogenatable hydrocarbon to produce a product containing the same number of carbon atoms but fewer hydrogen atoms. In another aspect, the present invention includes a method of dehydrogenating normal paraffin hydrocarbons containing 4 to 30 carbon atoms per molecule to the correspond ing normal mono-olefins with minimum production of side products. Yet another aspect of the present invention involves a novel catalytic composite comprising a combination of catalytically effective amounts of a platinum group component, a germanium component, and an alkali or alkaline earth component with a porous carrier material, which composite has highly preferred characteristics of activity, selectivity, and stability when it is employed in the dehydrogenation of dehydrogenatable hydrocarbons such as aliphatic hydrocarbons, naphthenic hydrocarbons and alkylaromatic hydrocarbons.

The dehydrogenation of dehydrogenatable hydrocarbons is an important commercial process because of the great and expanding demand for dehydrogenated hydrocarbons for use in the manufacture of various chemical products such as detergents, plastics, synthetic rubbers, pharmaceutical products, high octane gasoline, perfumes, drying oils, ion-exchange resins, and various other products well known to those skilled in the art. One example of this demand is in the manufacture of high octane gasoline by using C and C mono-olefins to alkylate isobutane. Another example of this demand is in the area of dehydrogenation of normal parafiin hydrocarbons to produce normal mono-olefins having 4 to 30 carbon atoms per molecule. These normal mono-olefins can, in turn, be utilized in the synthesis of vast numbers of other chemical products. For example, derivatives of normal monoolefins have become of substantial importance to the detergent industry where they are utilized to alkylate an alkylatable aromatic such as benzene, with resultant transformation of the product arylalkane into a wide variety of biodegradable detergents such as the alkylaryl sulfonate type of detergent which is most widely used today for household, industrial, and commercial processes. Still another large class of detergents produced from these normal mono-olefins are the oxyalkylated phenol derivatives in which the alkyl phenol base is prepared by the alkylation of phenol with these normal mono-olefins. Still another type of detergent produced from these normal monoolefins is a biodegradable alkylsulfate formed by the direct sulfation of the normal mono-olefin. Likewise, the olefin can be subjected to direct sulfonation with sodium bisulfite to make biodegradable alkylsulfonates. As a further example, these mono-olefins can be hydrated to produce alcohols which then, in turn, can be used to produce plasticizers and/ or synthetic lube oils.

Regarding the use of products made by the dehydrogenation of alkylaromatic hydrocarbons, these find wide application in industries including the petroleum, petrochemical, pharmaceutical, detergent, plastic industries, and the like. For example, ethylbenzene is dehydrogenated to produce styrene which is utilized in the manufacture of polystyrene plastics, styrene-butadiene rubber, and the like products. Isopropylbenzene is dehydrogenated to form alphamethyl styrene which, in turn, is extensively used in polymer formation and in the manufacture of drying oils, ion-exchange resins, and the like material.

Responsive to this demand for these dehydrogenation products, the art has developed a number of alternative methods to produce them in commercial quantities. One method that is widely utilized involves the selective dehydrogenation of dehydrogenatable hydrocarbons by contacting the hydrocarbons with a suitable catalyst at dehydrogenation conditions. As is the case with most catalytic procedures, the prinicpal measure of effectiveness for this dehydrogenation method involves the ability to perform its intended function with minimum interference of side reactions for extended periods of time. The analytical terms used in the art to broadly measure how well a particular catalyst per-forms its intended functions in a particular hydrocarbon conversion reaction are activity, selectivity, and stability, and for purposes of discussion here these terms are generally defined for a given reactant as follows: 1) activity is a measure of the catalysts ability to convert the hydrocarbon reactant into products at a specified severity level where severity level means the conditions usedthat is, the temperature, pressure, contact time, and presence of diluents such as H (2) selectivity usually refers to the amount of desired product or products obtained relative to the amount of the reactant converted; (3) stability refers to the rate of change with time of the activity and selectivity parametersobviously the smaller rate implying the more stable catalyst. More specifically, in a dehydrogenation process, activity commonly refers to the amount of conversion that takes place for a given dehydrogenatable hydrocarbon at a specified severity level and is typically measured on the basis ofdisappearance of the dehydrogenatable hydrocarbon; selectivity is typically measured by the amount, calculated on a mole percent of converted dehydrogenatable hydrocarbon basis, of the desired dehydrogenated hydrocarbon obtained at the particular severity level; and stability is typically equated to the rate of change with time of activity as measured by disappearance of the dehydrogenatable hydrocarbon and of selectivity as measured by the amount of desired hydrocarbon produced. Accordingly, the major problem facing workers in the hydrocarbon dehydrogenation art is the development of a more active and selective catalytic composite that has good stability characteristics.

I have now found a catalytic composite which possesses improved activity, selectivity, and stability when it is employed in a process for the dehydrogenation of dehydrogenatable hydrocarbons. In particular, I have determined that a combination of catalytically effective amounts of a platinum group component, a germanium component, and an alkali or alkaline earth component with a porous, refractory carrier material enables the performance of a dehydrogenation process to be substantially improved. Moreover, particularly good results are obtained when this composite is utilized in the dehydrogenation of long chain normal paraffins to produce the corresponding normal mono-olefins with minimization of side reactions such as skeletal isomerization, aromatization and cracking.

It is, accordingly, one object of the present invention to provide a novel method for dehydrogenation of dehydrogenatable hydrocarbons utilizing a catalytic composite containing a platinum group component, a germanium component, or an alkali or alkaline earth component combined with a porous carrier material. A second object is to provide a novel catalytic composite having superior performance characteristics when utilized in a dehydrogenation process. Another object is to provide an improved method for the dehydrogenation of normal paraffin hydrocarbons to produce normal mono-olefins. Yet another object is to improve the performance of a platinumcontaining dehydrogenation catalyst by using a relatively inexpensive component, germanium, to beneficially interact with the platinum metal.

In brief summary, one embodiment of the present invention involves a method for dehydrogenating a dehydrogenatable hydrocarbon which comprises contacting the hydrocarbon at dehydrogenation conditions with a catalytic composite comprising a combination of a platinum group component, a germanium component, and an alkali or alkaline earth component with a porous carrier material. The catalytic composite contains these components in amounts, calculated on an elemental basis, of about 0.01 to about 2 wt. percent of the platinum group metal, about 0.01 to about 5 wt. percent germanium, and about 0.1 to about 5 wt. percent of the alkali or alkaline earth metal.

A second embodiment relates to the dehydrogenation method described above in the first embodiment wherein the dehydrogenatable hydrocarbon is an aliphatic compound containing 2 to 30 carbon atoms per molecule.

A third embodiment relates to a novel catalytic composite containing a combination of a platinum group component, a germanium component or an alkali or alkaline earth component with a porous carrier material. These components are present in this composite in amounts sufiicient to result in the composite containing, on an elemental basis, about 0.01 to about 2 wt. percent of platinum group metal, 0.01 to about 5 wt. percent germanium, and about 0.1 to about 5 wt. percent of the alkali or alkaline earth metal.

Other objects and embodiments of the present invention concern specific details regarding essential and preferred catalytic ingredients, preferred concentration of components in the composite, suitable methods of composite preparation, suitable dehydrogenatable hydrocarbons, operating conditions for use in the dehydrogenation process, and the like particulars. These are hereinafter given in the following detailed discussion of each of these facets of the present invention.

Regarding the dehydrogenatable hydrocarbon that is subjected to the method of the present invention, it can, in general, be an organic compound having 2 to 30 carbon atoms per molecule and containing at least 1 pair of adjacent carbon atoms having hydrogen attached thereto. That is, it is intended to include within the scope of the present invention the dehydrogenation of any organic compound capable of being dehydrogenated to produce products containing the same number of carbon atoms but fewer hydrogen atoms, and capable of being vaporized at the dehydrogenation temperatures used herein. More particularly, suitable dehydrogenatable hydrocarbons are: aliphatic compounds containing 2 to 30 carbon atoms per molecule, alkylaromatic hydrocarbons where the alkyl group contains 2 to 6 carbon atoms, and naphthenes or alkyl-substituted naphthenes. Specific examples of suitable dehydrogenatable hydrocarbons are: (l) alkanes such as ethane, propane, n-butane, isobutanes, n-pentane, isopentane, neopentane, n-hexane, Z-methylpentane, 2,2-

dimethylbutane, n-heptane, 2 methylhexane, 2,2,3-trimethylbutane, and the like compounds; (2) naphthenes such as cyclopentane, methylcyclopentane, ethylcyclopentane, n-propylcyclopentane, cyclohexane, isopropylcyclopentane, 1,3 dimethylcyclohexane, and the like compounds; and (3) alkylaromatics such as ethylbenzene, npropylbenzene, n-butylbenzene, 1,3,5-triethylbenzene, isopropylbenzene, isobutylbenzene, ethylnaphthalene, and the like compounds.

In a preferred embodiment, the dehydrogenatable hydrocarbon is a normal parafiin hydrocarbon having about 4 to about 30 carbon atoms per molecule. For example, normal paraffin hydrocarbons containing about 10 to 15 carbon atoms per molecule are dehydrogenated by the subject method to produce the corresponding normal mono-olefin which can, in turn, be alkylated with benzene and sulfonated to make alkylbenzene sulfonate detergents having superior biodegradability. Likewise, n-alkanes having 12 to 18 carbon atoms per molecule can be dehydrogenated to the corresponding normal mono-olefin which, in turn, can be sulfated or sulfonated to make excellent detergents. Similarly, n-alkanes having 6 to 10 carbon atoms per molecule can be dehydrogenated to form the corresponding mono-olefins which can, in turn, be hydrated to produce valuable alcohols. Preferred feed streams for the manufacture of detergent intermediates contain a mixture of 4 or 5 adjacent normal paraffin homologues such as C to C13, C to C C to C and the like mixtures.

An essential feature of the present invention involves the use of a catalytic composite comprising a combination of catalytically effective amounts of a platinum group component, a germanium component, and an alkali or alkaline earth component with a porous carrier material.

Considering first the porous carrier material utilized in the present invention, it is preferred that the material be a porous, adsorptive, high surface area support having a surface area of about 25 to about 500 m. /gm. The porous carrier material should be relatively refractory to the conditions utilized in the dehydrogenation process, and it is intended to include within the scope of the present invention carrier materials which have traditionally been utilized in hydrocarbon conversion catalysts such as: (1) activated carbon, coke, or charcoal; (2) silica or silica gel, silicon carbide, clays, and silicates including those synthetically prepared and naturally occurring, which may or may not be acid treated, for example, Attapulgus clay, china clay, diatomaceous earth, fullers earth, kaolin, kieselguhr, etc.; (3) ceramics, porcelain, crushed firebrick, bauxite; (4) refractory inorganic oxides such as alumina, titanium dioxide, zirconium dioxide, chromium oxide, zinc oxide, magnesia, thoria, boria, silica-alumina, silica-magnesia, chromia-alumina, alumina-boria, silica-zirconia, etc.; (5) crystalline aluminosilicates such as naturally occurring or synthetically prepared mordenite and/or faujasite, either in the hydrogen form or in a form which has been treated with multivalent cations; and, (6) combinations of these groups. The preferred porous carrier materials for use in the present invention are refractory inorganic oxides, with best results obtained with an alumina carrier material. Suitable alumina materials are the crystalline aluminas known as the gamma-, eta-, and thetaalumina with gammaor eta-alumina giving best results. In addition, in some embodiments the alumina carrier material may contain minor proportions of other well known refractory inorganic oxides such as silica, zirconia, magnesia, etc.; however, the preferred support is substantially pure gammaor eta-alumina. Preferred carrier materials have an apparent bulk density of about 0.3 to about 0.7 gm./cc. and surface area characteristics such that the average pore diameter is about 20 to 3000 angstroms, the pore volume is about 0.1 to about 1 mL/gm. and the surface area is about to about 500 m. gm. In general, best results are typically obtained with a gamma-alumina carrier material which is used in the form of spherical particles having: a realtively small diameter (i.e., typically about inch), an apparent bulk density of about 0.5 gm./cc, a pore volume of about 0.4 mL/gm. and a surface area of about 175 m. gm.

The preferred alumina carrier material may be prepared in any suitable manner and may be synthetically prepared or naturally occurring. Whatever type of alumina is employed it may be activated prior to use by one or more treatments including drying, calcination, steaming, etc., and it may be in a form known as activated alumina, activate-d alumina of commerce, porous alumina, alumina gel, etc. For example, the alumina carrier may be prepared by adding a suitable alkaline reagent, such as ammonium hydroxide to a salt of aluminum such as aluminum chloride, aluminum nitrate, etc., in an amount to form an aluminum hydroxide gel which upon drying and calcining is converted to alumina. The alumina carrier may be formed in any desired shape such as spheres, pills, cakes, extrudates, powders, granules, etc., and utilized in any desired size. For the purpose of the present invention a particularly preferred form of alumina is the sphere; and alumina spheres may be continuously manufactured by the well known oil drop method which comprises: forming an alumina hydrosol by any of the techniques taught in the art and preferably by reacting alumina metal with hydrochloric acid, combining the resulting hydrosol with a suitable gelling agent and dropping the resultant mixture into an oil bath maintained at elevated temperatures. The droplets of the mixture remain in the oil bath until they set and form hydrogel spheres. The spheres are then continuously withdrawn from the oil bath and typically subjected to specific aging treatments in oil and an ammoniacal solution to further improve their physical characteristics. The resulting aged and gelled particles are then washed and dried at a relatively low temperature of about 300 F. to about 400 F. and subjected to a calcination procedure at a temperature of about 850 F. to about 1300 F. for a period of about 1 to about 20 hours. It is also a good practice to subject the calcined particles to a high temperature steam treatment in order to remove as much as possible of undesired acidic components. This manufacturing procedure effects conversion of the alumina hydrogel to the corresponding crystalline gamma-alumina. See the teachings of US. Pat. No. 2,620,314 for additional details.

One essential constituent of the catalyst of the present invention is a germanium component. This component may be present in the composite as an elemental metal or as a chemical compound such as the corresponding oxide, sulfide, oxychloride, halide, etc., and it may be utilized in any amount which is catalytically effective. Best results are, in general, obtained when this component is present in an oxidation state above that of the elemental metal; for example, as germanium dioxide. In addition, it is preferred to have the germanium component uniformly distributed throughout the carrier material. Preferably this component is used in an amount sufiicient to result in the final catalytic composite containing, on an elemental basis, 0.01 to about 5 wt. percent germanium, with best results typically obtained with about 0.05 to about 2 wt. percent germanium. This component may be incorporated in the catalytic composite in any suitable manner such as by coprecipitation or cogellation with the porous carrier material, ion-exchange with the carrier material or impregnation of the carrier material at any step in the preparation. It is understood that it is intended to include within the scope of the present invention all conventional methods for incorporating a metallic component in a catalytic composite, and the particular method of incorporation used is not deemed to be an essential feature of the present invention. One acceptable method of incorporating the germanium component into the catalytic composite involves coprecipitating the germanium component during the preparation of the preferred carrier material,

alumina. This method typically involves the addition of a suitable soluble, decomposable germanium compound, such as germanium tetrachloride, to the aluminum hydrosol. Then the resulting mixture of the germanium compound and hydrosol is combined with a suitable gelling agent and dropped into an oil bath, etc., as explained in detail hereinbefore. After drying and calcining the resulting gelled carrier material there is obtained an intimate combination of alumina and gennanium oxide. A preferred method of incorporating the germanium component involves utilization of a soluble, decomposable compound of germanium to impregnate the porous carried material. The solvent used in this impregnation step is generally selected on the basis of the capability to dissolve the selected germanium compound; typically, it is an aqueous, acidic solution. Thus, the germanium component may be added to the carrier material by commingling the latter with an aqueous, acidic solution of a suitable germanium salt or compound of germanium such as germanium tetrachloride, germanium difiuoride, germanium tetrafiuoride, germanium di-iodide, germanium monosulfide and the like compounds. A particularly preferred impregnation solution comprises, germanium metal dissolved in chlorine Water. In general, the germanium component can be impregnated either prior to, simultaneous with, or after the platinum group component is added to the carrier material. However, I have found excellent results when the germanium component is impregnated simultaneously with the platinum group component. In fact, one preferred impregnation solution contains chloroplatinic acid, nitric acid, and germanium metal dissolved in chlorine water. Following the incorporation of the germanium component, the resulting composite is typically dried and calcined as explained hereinafter.

A second essential constituent for the catalytic composite used in the present invention is a platinum group component. Although the process of the present invention is specifically directed to the use of a catalytic composite containing platinum, it is intended to include other platinum group metals, such as palladium, rhodium, ruthenium, osmium, and iridium. The platinum group metallic component such as platinum may exist within the final catalytic composite as a compound such as the oxide, sulfide, halide, etc., or as an elemental metal. Generally, the amount of the platinum group metallic component present in the final catalyst is small compared to the quantities of the other components combined therewith. In fact, the platinum group metallic component generally comprises about 0.01 to about 2% by weight of the final catalytic composite calculated on an elemental basis. Excellent results are obtained when the catalyst contains about 0.05 to about 1 wt. percent of the platinum group metal. The preferred platinum group component is platinum or a compound of platinum.

The platinum group metallic component may be incorporated in the catalytic composite in any suitable manner such as coprecipitation or cogellation with the carrier material, ion-exchange with the carrier material and/or hydrogel, or impregnation either after or before calcination of the carrier material, etc. The preferred method of peparing the catalyst involves the utilization of a soluble, decomposable compound of the platinum group metal to impregnate the porous carrier material. For example, the platinum group metal may be added to the carrier by commingling the latter with an aqueous solution of chloroplatinic acid. Other water-soluble compounds of the platinum group metals may be employed in impregnation solutions and include ammonium chloroplatinate, bromoplatinic acid, platinum chloride, dinitrodiaminoplatinum, palladium chloride, palladium nitrate, palladium sulfate, diamine palladium hydroxide, tetraminepalladium chloride, etc. The utilization of a platinum chloride compound such as chloroplatinic acid is ordinarily preferred. In addition, it is generally preferred to impregnate the carrier material after it has been calcined in order to minimize the risk of washing away the valuable platinum metal compounds; however, in some cases it may be advantageous to impregnate the carrier when it is in a gelled state. Following the incorporation of the platinum group component, the resulting composite is typically dried and subjected to a high temperature calcination as explained hereinafter.

Another essential constituent of the catalyst used in the present invention is the alkali or alkaline earth component. More specifically, this component is selected from the group consisting of the compounds of the alkali metalscesium, rubidium, potassium, sodium, and lithiumand of the alkaline earth metals-calcium, strontium, barium, and magnesium. This component may exist within the catalytic composite as a relatively stable compound such as the oxide or sulfide, or in combination with one or more of the other components of the composite, or in combination with the carrier material such as, for example, in the form of a metal aluminate. Since, as is explained hereinafter, the composite containing the alkali or alkaline earth is always calcined in an air atmosphere before use in the conversion of hydrocarbons, the most likely state this component exists in during use in dehydrogenation is the metallic oxide. Regardless of what precise form in which it exists in the composite, the amount of this component utilized is preferably selected to provide a composite containing about 0.1 to about wt. percent of the alkali or alkaline earth metal, and, more preferably, about 0.25 to about 3.5 wt. percent. Best results are ordinarily obtained when this component is a compound of lithium or potassium.

This alkali or alkaline earth component may be com bined with the porous carrier material in any manner known to those skilled in the art such as by impregnation, coprecipitation, physical mixture, ion-exchange and the like procedures. However, the preferred procedure involves impregnation of the carrier material either before, during or after it is calcined, or before, during or after the platinum group and germanium components are added to the carrier material. Best results are ordinarily obtained when this component is added to the carrier material after the platinum group and germanium components because the alkali metal or alkaline earth metal acts to neutralize some of the acid used in the preferred impregnation procedure for these metallic components. In fact, it is preferred to add the platinum group and germanium components to the carrier material, oxidize the resulting composite at a high temperature (i.e., typically about 800 to 1000" F.), then treat the resulting oxidized composite with a mixture of air and steam in order to remove residual acidity, and thereafter add the alkali metal or alkaline earth component. Typically, the impregnation of the carrier material with this component is performed by contacting the carrier material with a solution of a suitable decomposable compound or salt of the desired alkali or alkaline earth metal. Hence, suitable compounds include the alkali metal or alkaline earth metal halides, sulfates, nitrates, acetates, carbonates, phosphates and the like compounds. For example, excellent results are obtained by impregnating the carrier material after the platinum group and germanium components have been combined therewith, with an aqueous solution of lithium nitrate or potassium nitrate. Following the addition of this component, the resulting composite is dried and calcined in an air stream as is subsequently discussed.

Regarding the preferred amounts of the various metallic components of the subject catalyst, I have found it to be a good practice to specify the amounts of germanium component and of the alkali or alkaline earth component as a function of the amount of the platinum group component. On this basis, the amount of the germanium component is ordinarily selected so that the atomic ratio of the germanium metal to the platinum group metal contained in the composite is about 0.1:1 to about :1,

with the preferred range being about 0.2:1 to about 5:1. Similarly, the amount of the alkali or alkaline earth component is ordinarily selected to produce a composite containing an atomic ratio of alkali or alkaline earth metal to the platinum group metal of about 5: 1 to about 50:1 or more, with the preferred range being about 10:1 to about 25:1.

Another significant parameter for the subject catalyst is the total metals content which is defined to be the sum of the platinum group component, the germanium component, and alkali or alkaline earth component, calculated on an elemental metal basis. Good results are ordinarily obtained with the subject catalyst when this parameter is fixed at a value of from 0.12 to about 12 wt. percent with best results ordinarily achieved at a metals loading of about 0.5 to about 5.5 wt. percent.

Integrating the above discussion of each of the essential components of the catalytic composite used in the present invention, it is evident that a particularly preferred catalytic composite comprises a combination of a platinum component, a germanium component and an alkali or alkaline earth component 'with an alumina carrier material in amounts sufiicient to result in the composite containing from about 0.05 to about 1 Wt. percent platinum, about 0.05 to about 2 wt. percent germanium, and about 0.25 to about 3.5 wt. percent of the alkali or alkaline earth metal. Accordingly, specific examples of especially preferred catalyst composites are as follows: (1) a catalytic composite comprising 0.75 wt. percent platinum, 0.5 wt. percent germanium, and 0.5 wt. percent lithium combined with an alumina carrier material; (2) a catalytic composite comprising 0.65 wt. percent platinum, 0.1 wt. percent germanium, and 2.8 wt. percent potassium combined with an alumina carrier material; (3) a catalytic composite comprising 0.375 wt. percent platinum, 0.375 wt. percent germanium, and 0.5 wt. percent lithium combined with an alumina carrier material; (4) a catalytic composite comprising 0.5 wt. percent platinum, 1 wt. percent germanium, and 2.8 wt. percent potassium combined with an alumina carrier material; (5) a catalytic composite comprising 0.375 wt. percent platinum, 0.25 wt. percent germanium, and 0.5 wt. percent lithium combined with an alumina carrier material; (6) a catalytic composite comprising 0.375 wt. percent platinum, 0.5 wt. percent germanium, and 2.8 wt. percent potassium combined with an alumina carrier material.

Regardless of the details of how the components of the catalyst are combined with the porous carrier material, the resulting composite generally will be dried at a temperature of about 200 F. to about 600 F. for a period of from about 2 to 24 hours or more, and finally calcined at a temperature of about 600 F. to about 1100 F. in an air atmosphere for a period of about 0.5 to 10 hours, preferably about 1 to about 5 hours, in order to substantially convert the metalic components to the oxide form. When acidic components are present in any of the reagents used to effect incorporation of any one of the components of the subject composite, it is a good practice to subject the resulting composite to a high temperature treatment with steam or with mixture of steam and air, either after or before the calcination step described above, in order to remove as much as possible of the undesired acidic component. For example, when the platinum group component is incorporated by impregnating the carrier material with chloroplatinic acid, it is preferred to subject the resulting composite to a high temperature treatment with steam in order to remove as much as possible of the undesired chloride.

It is preferred that the resultant calcined catalytic composite be subjected to a substantially water-free reduction prior to its use in the conversion of hydrocarbons. This step is designed to insure a uniform and finely divided dispersion of the metallic components throughout the carrier material. Preferably, substantially pure and dry hydrogen (i.e., less than 20 vol. p.p.m. H O) is used as the reducing agent in this step. The reducing agent is contacted with the calcined composite at a temperature of about 800 F. to about 1200 F. and for a period of time of about 0.5 to hours or more, effective to substantially reduce at least the platinum group component. As indicated hereinbefore, the germanium component is believed to remain in a positive oxidation state during this reduction step. This reduction treatment may be performed in situ as part of a start-up sequence if precautions are taken to predry the plant to a substantially water-free state and if substantially water-free hydrogen is used.

Although it is not essential, the resulting reduced catalytic composite may, in some cases, be beneficially subjected to a presulfiding operation designed to incorporate in the catalytic composite from about 0.05 to about 0.50 wt. percent sulfur calculated on an elemental basis. Preferably, this presulfiding treatment takes place in the presence of hydrogen and a suitable sulfur-containing compound such as hydrogen sulfide, lower molecular 'weight mercaptans, organic sulfides, etc. Typically, this procedure comprises treating the reduced catalyst with a sulfiding gas such as a mixture containing a mole ratio of Hg to H 'S of about 10:1 at conditions sufficient to effect the desired incorporation of sulfur, generally including a temperature ranging from about 50 F. up to about 1100" F. or more. This presulfiding step can be performed in situ or ex situ.

According to the method of the present inventipn, the dehydrogenatable hydrocarbon is contacted with a catalytic composite of the type described above in a dehydrogenation zone at dehydrogenation conditions. This contacting may be accomplished by using the catalyst in a fixed bed system, a moving bed system, a fluidized bed system, or in a batch type operation; however, in view of the danger of attrition losses of the valuable catalyst and of well known operational advantages, it is preferred to use a fixed bed system. In this system, the hydrocarbon feed stream is preheated by any suitable heating means to the desired reaction temperature and then passed into a dehydrogenation zone containing a fixed bed of the catalyst type previously characterized. -It is, of course, understood that the dehydrogenation zone may be one or more separate reactors with suitable heating means therebetween to insure that the desired conversion temperature is maintained at the entrance to each reactor. It is also to be noted that the reactants may be contacted with the catalyst bed in either upward, downward, or radial flow fashion, with the latter being preferred. In addition, it is to be noted that the reactants may be in the liquid phase, a mixed liquid-vapor phase, or a vapor phase when they contact the catalyst, wtih best results obtained in the vapor phase.

Although hydrogen is the preferred diluent for use in the subject dehydrogenation method, in some cases other art-recognized diluents may be advantageously utilized such as steam, methane, carbon dioxide, and the like diluents. Hydrogen is preferred because it serves the dualfunction of not only lowering the partial pressure of the dehydrogenatable hydrocarbon, but also of suppressing the formation of hydrogen-deficient, carbonaceous deposits on the catalytic composite. Ordinarily, hydrogen is utilized in amounts sufficient to insure a hydrogen to hydrocarbon mole ratio of about 1:1 to about :1, with best results obtained in the range of about 1.5:1 to about 10:1. The hydrogen stream charged to the dehydrogenation zone will typically be recycle hydrogen obtained from the efiiuent stream from this zone after a suitable separation step.

Regarding the conditions utilized in the process of the present invention, these are generally selected from the conditions well known to those skilled in the art for the particular dehydrogenatable hydrocarbon which is charged to the process. More specifically, suitable conversion temperatures are selected from the range of about 700 to about 1250 F., with a value being selected from the 10 lower portion of this range for the more easily dehydrogenated hydrocarbons such as the long chain normal parafiins and from the higher portion of this range for the more difiicultly dehydrogenated hydrocarbons such as propane, butane, and the like hydrocarbons. For example, for the dehydrogenation of C to C normal paraffius, best results are ordinarily obtained at a temperature of about 800 to about 950 F. The pressure utilized is ordinarily selected at a value which is as low as possible consistent with the maintenance of catalyst stability, and is usually about 0.1 to about 10 atmospheres, with best results ordinarily obtained in the range of about .5 to about 3 atmospheres. In addition, a liquid hourly space velocity (calculated on the basis of the volume amount, as a liquid, of hydrocarbon charged to the dehydrogenation zone per hour divided by the volume of the catalyst bed utilized) is selected from the range of about 1 to about 40 hr.- with best results for the dehydrogenation of long chain normal parafiins typically obtained at a relatively high space velocity of about 25 to 35 hrr Regardless of the details concerning the operation of the dehydrogenation step, an effluent stream will be withdrawn therefrom. This efiiuent Will contain unconverted dehydrogenatable hydrocarbons, hydrogen, and products of the dehydrogenation reaction. This stream is typically cooled and passed to a separating zone wherein a hydrogen-rich vapor phase is allowed to separate from a hydrocarbon-rich liquid phase. In general, it is usually desired to recover the unreacted dehydrogenatable hydrocarbon from this hydrocarbon-rich liquid phase in order to make the dehydrogenation process economically attractive. This recovery step can be accomplished in any suitable manner known to the art such as by passing the hydrocarbon-rich liquid phase through a bed of suitable adsorbent material which has the capability to selectively retain the dehydrogenated hydrocarbons contained therein or by contacting same with a solvent having a high selectivity for the dehydrogenated hydrocarbon or by a suitable fractionation scheme where feasible. In the case where the dehydrogenated hydrocarbon is a mono-olefin, suitable adsorbents having this capability are activated silica gel, activated carbon, activated alumina, various types of specially prepared molecular sieves, and the like adsorbents. In another typical case, the dehydrogenated hydrocarbons can be separated from the unconverted dehydrogenatable hydrocarbons by utilizing the inherent capability of the dehydrogenated hydrocarbons to easily enter into several well known chemical reactions such as alkylation, oligomerization, halogenation, sulfonation, hydration, oxidation, and the like reactions. Irrespective of how the dehydrogenated hydrocarbons are separated from the unreacted hydrocarbons, a stream containing the unreacted dehydrogenatable hydrocarbons will typically be recovered from this hydrocarbon separation step and recycled to the dehydrogenation step. Likewise, the hydrogen phase present in the hydrogen separating zone will be withdrawn therefrom, a portion of it vented from the system in order to remove the net hydrogen make, and the remaining portion is typically recycled, through suitable compressing means, to the dehydrogenation step in order to provide diluent hydrogen therefor.

In a preferred embodiment of the present invention wherein long chain normal parafiin hydrocarbons are dehydrogenated to the corresponding normal mono-olefins, a preferred mode of operation of this hydrocarbon separation step involves an alkylation reaction. In this mode, the hydrocarbon-rich liquid phase withdrawn from the separating zone is combined with a stream containing an alkylatable aromatic and the resulting mixture passed to an alkylation zone containing a suitable highly acidic catalyst such as an anhydrous solution of hydrogen fluoride. In the alkylation zone the mono-olefins react with the alkylatable aromatic while the unconverted normal parafiins remain substantially unchanged. The efiiuent stream from the alkylation zone can then be easily sepa- 1 1 rated, typically by means of a suitable fractionation system, to allow recovery of the unreacted normal parafiins. The resulting stream of unconverted normal paraffins is then usually recycled to the dehydrogenation step of the present invention.

The following working examples are introduced to illustrate further the novelty, mode of operation, utility, and benefits associated with the dehydrogenation method and catalytic composite of the present invention. These examples are intended to be illustrative rather than restrictive.

These examples are all performed in a laboratory scale dehydrogenation plant comprising a reactor, a hydrogen separating zone, a heating means, cooling means, pumping means, compressing means, and the like equipment. In this plant, the feed stream containing the dehydrogenatable hydrocarbon is combined with a hydrogen stream and the resultant mixture heated to the desired conversion temperature, which refers herein to the temperature maintained at the inlet to the reactor. The heated mixture is then passed into contact with the catalyst which is maintained as a fixed bed of catalyst particles in the reactor. The pressures reported herein are recorded at the outlet from the reactor. An efiluent stream is withdrawn from the reactor, cooled, and passed into the separating zone wherein a hydrogen gas phase separates from a hydrocarbon-rich liquid phase containing dehydrogenated hydrocarbons, unconverted dehydrogenatable hydrocarbons and a minor amount of side products of the dehydrogenation reaction. A portion of the hydrogen-rich gas phase is recovered as excess recycle gas with the remaining portion being continuously recycled through suitable compressive means to the heating zone as described above. The hydrocarbon-rich liquid phase from the separating zone is withdrawn therefrom and subjected to analysis to determine conversion and selectivity for the desired dehydrogenated hydrocarbon as will be indicated in the examples. Conversion numbers of the dehydrogenatable hydrocarbon reported herein are all calculated on the basis of disappearance of the dehydrogenatable hydrocarbon and are expressed in mole percent. Similarly, selectivity numbers are reported on the basis of moles of desired hydrocarbon produced per 100 moles of dehydrogenatable hydrocarbon converted.

All of the catalysts utilized in these examples are prepared according to the following general method with suitable modifications in stoichiometry to achieve the compositions reported in each example. First, an alumina carrier material comprising A inch spheres is prepared by: forming an aluminum hydroxyl chloride sol by dissolving substantially pure aluminum pellets in a hydrochloric acid solution, adding hexamethylenetetramine to the sol, gelling the resulting solution by dropping it into an oil bath to form spherical particles of an alumina hydrogel, aging, and washing the resulting particles with an ammoniacal solution and finally drying, calcining, and steaming the aged and washed particles to form spherical particles of gamma-alumina containing substantially less than 0.1 wt. percent combined chloride. Additional details as to this method of preparing this alumina carrier material are given in the teachings of US. Pat. No. 2,620,314.

Second, a measured amount of germanium dioxide powder is placed in a porcelain boat and subjected to a reduction treatment with substantially pure hydrogen at a temperature of about 650 C. for about 2 hours. The resulting grayish-black solid material is dissolved in chlorine water to form a solution. An aqueous solution containing chloroplatinic acid and nitric acid is also prepared. The two solutions are then intimately admixed and used to impregnate the gamma-alumina particles. The amounts of the various reagents are carefully selected to yield final catalytic composites containing the required amounts of platinum and germanium. In order to insure uniform distribution of metallic components throughout the carrier material, this impregnation step is performed by adding the alumina particles to the impregnation mixture with constant agitation. The impregnation mixture is maintained in contact with the alumina particles for a period of about /2 hour at a temperature of 70 F. thereafter, the temperature of the impregnation mixture is raised to about 225 F. and the excess solution is evaporated in a period of about one hour. The resulting dried particles are then subjected to a calcination treatment in an air atmosphere at a temperature of about 500 to about 1000 F. for about 2 to 10 hours. Thereafter, the resulting calcined particles are treated with an air stream containing from about 10 to about 30% steam at a temperature of about 800 to about 1000 F. for an additional period from about 11 to about 5 hours in order to further reduce the residual combined chloride in the composite.

Finally, the alkali or alkaline earth metal component is added to the resulting calcined particles in a second impregnating step. This second impregnation step involves contacting the calcined particles with an aqueous solution of a suitable decomposable salt of the desired alkali or alkaline earth component. For the composites utilized in the present examples, the salt is either lithium nitrate or potassium nitrate. The amount of this salt is carefully chosen to result in a final composite having the desired composition. The resulting alkali impregnated particles are then dried, calcined and steamed in exactly the same manner as described above following the first impregnation step.

In all the examples the catalyst is reduced during startup by contacting with hydrogen at an elevated tempera ture and thereafter sulfided with a mixture of H and H 5.

EXAMPLE I The reactor is loaded with 100 cc. of a catalyst containing, on an elemental basis, 0.375 wt. percent platinum, 0.25 wt. percent germanium, 0.5 wt. percent lithium, and less than 0.15 wt. percent chloride. The feed stream utilized is commercial grade isobutane containing 99.7 Wt. percent isobutane and 0.3 wt. percent normal butane. The feed stream is contacted with the catalyst at a temperature of 1065 F., a pressure of 10 p.s.i.g., a liquid hourly space velocity of 4.0 hr. and a hydrogen to hydrocarbon mole ratio of 2:1. The dehydrogenation plant is lined-out at these conditions and a 20 hour test period commenced. The hydrocarbon product stream from the plant is continuously analyzed by GLC (gasliquid chromatography) and a high conversion of isobutane is observed with a selectivity for isobutylene of at least EXAMPLE II The catalyst contains, on an elemental basis, 0.375 wt. percent platinum, 0.5 Wt. percent germanium, 0.5 wt. percent lithium, and less than 0.15 wt. percent combined chloride. The feed stream is commercial grade normal dodecane. The dehydrogenation reactor is operated at a temperature of 870 F., a pressure of 10 p.s.i.g., a liquid hourly space velocity of 32 hr.- and a hydrogen to hydrocarbon mole ratio of 8:1. After a line-out period, a 20 hour test period is performed during which the average conversion of the normal dodecane is maintained at a high level with a selectivity for normal dodecene of about EXAMPLE III The catalyst is the same as utilized in Example II. The feed stream is normal tetradodecane. The conditions utilized are a temperature of 840 F., a pressure of 20 p.s.i.g., a liquid hourly space velocity of 32 hr.*, and a hydrogen to hydrocarbon mole ratio of 8:1. After a lineout period, a 20 hour test shows an average conversion of about 12% and a selectivity for normal tetrodecene of about 90%.

13 EXAMPLE IV The catalyst contains, on an elemental basis, 0.30 wt. percent platinum, 0.75 wt. percent germanium and 0.6 wt. percent lithium, with combined chloride being less than 0.2 Wt. percent. The feed stream is substantially pure normal butane. The conditions utilized are a temperature of 950 F, a pressure of I15 p.s.i.g., a liquid hourly space velocity of 4.0 hr. and a hydrogen to hydrocarbon mole ratio of 4:1. After a line-out period, a hour test is performed with the average conversion of the normal butane being about and the selectivity for normal butene is about EXAMPLE V The catalyst contains, on an elemental basis, 0.75 wt. percent platinum, 0.5 wt. percent germanium, 2.8 wt. percent potassium, and less than 0.2 wt. percent combined chloride. The feed stream is commercial grade ethylbenzene. The conditions utilized are a pressure of 15 p.s.i.g., a liquid hourly space velocity of 32 hr.- a temperature of 1050" F, and a hydrogen to hydrocarbon mole ratio of 8: 1. During a 20 hour test period, at least of equilibrium conversion of the ethylbenzene is observed. The selectivity for styrene is about 98%.

I claim as my invention:

1. A catalytic composite comprising a combination of a platinum group metal, a germanium component, and an alkali or alkaline earth component with a porous carrier material, wherein substantially all of said platinum groupmetal is present as the elemental metal and substantially all of said germanium component is present in an oxidation state above that of the elemental metal, and wherein the components are present in amounts sufiicient to result in the catalytic composite containing, on an elemental basis, about 0.01 to about 2 wt. percent of the platinum group metal, about 0.01 to about 5 wt. percent germanium, and about 0.1 to about 5 wt. percent of the alkali metal or alkaline earth metal.

2. A catalytic composite as defined in claim 1 wherein the platinum group metal is platinum.

3. A catalytic composite as defined in claim 1 wherein said porous carrier material is a refractory inorganic oxide.

4. A catalytic composite as defined in claim 3 wherein said refractory inorganic oxide is alumina.

5. A catalytic composite as defined in claim 1 wherein said alkali or alkaline earth metal component is a compound of lithium.

6. A catalytic composite as defined in claim 1 wherein said alkali or alkaline earth metal component is a compound of potassium.

7. A catalytic composite as defined in claim 1 wherein the atomic ratio of germanium to the platinum group metal contained in the composite is about 0.2:1 to about 5:1 and wherein the atomic ratio of alkali or alkaline earth metal to platinum group metal is about 10:1 to about 25:1.

8. A catalytic composite as defined in claim 1 wherein said platinum group metal is platinum, wherein said porous carrier material is alumina and wherein said components are present in amounts sufficient to result in the composite containing, on an elemental basis, about 0.05 to about 1 wt. percent platinum, about 0.05 to about 2 Wt. percent germanium and about 0.25 to about 3.5 wt. percent of the alkali or alkaline earth metal.

9. A catalytic composite as defined in claim 8 wherein said alkali or alkaline earth component is a compound of lithium.

10. A catalytic composite as defined in claim 8 wherein said alkali or alkaline earth component is a compound of potassium.

References Cited UNITED STATES PATENTS CURTIS R. DAVIS, Primary Examiner US. Cl. X.R. 260669, 683.3 

